Enhancing the Photocatalytic Reduction of O ₂ to H ₂ O ₂ Through Proton Enrichment on Covalent Organic Frameworks

Increasing the concentration of reagents in chemical reactions is crucial for improving reaction rates. In this study, which focused on the O 2 photocatalytic reduction as a model reaction, a targeted proton enrichment was achieved through the synergistic coordination of imine bonding and pyridazine functional groups in a covalent organic framework. This enhancement resulted in an increased supply of protons during O 2 reduction, leading to the efficient photocatalytic production of H 2 O 2 . The adjacent distribution of nitrogen atoms provides sites for proton enrichment, and the maintenance of the stability of the protons on the catalyst surface is facilitated by moderate intermolecular forces, thus enabling protons to participate in the O 2 reduction process. The specific reduction mode of the pyridazine functional group, whereby the adsorption of protons is followed by that of O 2 , has been shown to significantly enhance the transition from ·O 2 − to *OOH. The H 2 O 2 yield was determined to be 12,100 µmol g −1 h −1 , exhibiting a solar chemical conversion efficiency of 2.15%, which is the highest observed value for photocatalysts in pure water. This study provides new insights for improving the efficiency of photocatalytic H 2 O 2 production.